Catalina: after 10.15.6 update, the system became unstable, a lot of kernel panics. The system was stable before the update
After installing update 10.15.6 few days ago, since after the first reboot, the system became incredibly unstable. This machine (iMac (27-inch, Late 2013) contains only several VirtualBox machines running from years without problems. The problem seems to directly related to the 10.15.6 update, because the only effect post update is that the machine became unusable.
Following the forums, I have detached any external device like mouse, hard disks, but the problem persists. Sometimes the system live for minutes, some times for one/two hours. Any version of VirtualBox tested, from 5.x to 6.1.12, the system crash without reason. SSD disk is ok, RAM is ok, NVRAM cleared, Onyx passed. It would seem that the system allocates memory until exhaustion and gets stuck in kernel panic after the physical memory has been exceeded. The machine has 32GB and the VMs in total use 28GB, and until the update they had always worked very well.
Sample of kernel panic (from the hundreds that have happened in the last few days) ... :
panic(cpu 2 caller 0xffffff7f959dfad5): userspace watchdog timeout: no successful checkins from com.apple.WindowServer in 130 seconds
service: com.apple.logd, total successful checkins since load (10014 seconds ago): 1001, last successful checkin: 0 seconds ago
service: com.apple.WindowServer, total successful checkins since load (9984 seconds ago): 980, last successful checkin: 130 seconds ago
panic(cpu 2 caller 0xffffff7f8f7dfad5): userspace watchdog timeout: no successful checkins from com.apple.WindowServer in 138 seconds
service: com.apple.logd, total successful checkins since load (7930 seconds ago): 792, last successful checkin: 0 seconds ago
service: com.apple.WindowServer, total successful checkins since load (7900 seconds ago): 776, last successful checkin: 138 seconds ago
panic(cpu 2 caller 0xffffff7f86bdfa8d): watchdog timeout: no checkins from watchdogd in 98 seconds (1151 total checkins since monitoring last enabled)
panic(cpu 1 caller 0xffffff7f94efaaae): watchdog timeout: no checkins from watchdogd in 306 seconds (129 totalcheckins since monitoring last enabled), shutdown in progress
panic(cpu 1 caller 0xffffff7f841dfad5): userspace watchdog timeout: no successful checkins from com.apple.WindowServer in 120 seconds
service: com.apple.logd, total successful checkins since load (17840 seconds ago): 1784, last successful checkin: 0 seconds ago
service: com.apple.WindowServer, total successful checkins since load (17810 seconds ago): 1737, last successful checkin: 120 seconds ago
panic(cpu 3 caller 0xffffff801d42ee2f): "invalid commandSleep while not holding the gate"@/AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-6153.141.1/iokit/Kernel/IOCommandGate.cpp:323
panic(cpu 1 caller 0xffffff800322ee2f): "invalid commandSleep while not holding the gate"@/AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/xnu/xnu-6153.141.1/iokit/Kernel/IOCommandGate.cpp:323
iMac 27″, macOS 10.13